Nested loop error handling in batch script

Question

I have written a nested loop for file compare in batch script.

fc 1.txt 2.txt | findstr "no diff" 

IF %ERRORLEVEL% EQU 1 (

fc 3.txt 4.txt | findstr "no diff"

IF %ERRORLEVEL% EQU 1 (
echo 1
goto exit
) ELSE ( 
echo 2
goto exit )))

Logic to execute is: a. If 1&2 and 3&4 are different - echo 1

b. If 1&2 are different but not 3&4 - echo 2

While this code is working fine if there are no differences ie doesn't enter "if" condition. If I try to do requirement for echo 2, it is actually showing echo 1. Not sure how to correct this.

MC ND · Accepted Answer · 2015-01-13 13:13:16Z

When the parser prepares the lines or blocks of lines (lines in parenthesis), all the variable reads are replaced with the value in the variable before starting to execute the code, so your %errorlevel% check inside the first if will use the same errorlevel value that was used when all the block was parsed.

You can solve it using delayed expansion (setlocal enabledelayedexpansion) and replacing where needed the read operation in the variable from %var% into !var!, indicating to the parser that the read operation must be delayed until the execution of the command.

Or you can change the way to check for the errorlevel value, from if %errorlevel% equ ... into if errorlevel n that will be true if the errorlevel value is equal or greater than the indicated n value.

In this case it is using a language construct that does not involve variable read operations and is not affected by value replacements at parse time

fc 1.txt 2.txt >nul
if errorlevel 1 (
    fc 3.txt 4.txt >nul
    if errorlevel 1 (
        echo 1
    ) else (
        echo 2
    )
)

RGuggisberg · Accepted Answer · 2015-01-14 04:10:27Z

1

Here's another way to do it.

fc 1.txt 2.txt | findstr "no diff" && goto :done
fc 3.txt 4.txt | findstr "no diff" && (echo 2 & goto :done)
echo 1
:done

answered Jan 14, 2015 at 4:10

RGuggisberg

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